K12MATH007: Math Grade 7

Unit 3: Expressions and EquationsImagine you are keeping track of the growth of bacteria in a science
lab. You would like to make predictions based on the patterns you are
starting to see, but extending a table of values would take way too
long. One of the many goals of this unit will be to represent this
real-life data as an equation and then solve it.

In this unit, you will develop your algebraic skills by writing and
simplifying expressions using variables, numbers, and symbols. You will
extend these skills to equations with multiple steps, including
combining like terms and using the distributive property. Finally, you
will take all of these skills and use them to help represent and solve
real-life problems using equations and inequalities.

Unit 3 Time Advisory
Completing this unit should take approximately 14 hours and 15
minutes.

☐ Subunit 3.1: 1 hour and 15 minutes

☐ Subunit 3.2: 1 hour and 15 minutes

☐ Subunit 3.3: 1 hour

☐ Subunit 3.4: 3 hours and 15 minutes

☐ Subunit 3.5: 3 hours and 15 minutes

☐ Subunit 3.6: 4 hours and 15 minutes

Unit3 Learning Outcomes
Upon successful completion of this course, you will be able to:
- Write, simplify, and evaluate algebraic expressions.
- Solve and check multistep algebraic equations.
- Solve and graph inequalities with one variable.
- Model real-life situations using equations and inequalities.

3.1 Writing ExpressionsEquations are created by piecing together different expressions. In
this subunit, you will focus on changing descriptions of different
situations into mathematical expressions by converting words into
numbers, variables, and symbols.

Instructions: Complete this activity using the items and variables
given. The important point of this task is to make sense of the
expressions that you write. Be sure to think of how the different
expressions might be used to give real-life data.

Instructions: Read the lesson up to the “Time to Practice” section.
While you are reading through the examples, make a table with four
columns in your notes. The columns will be labeled “Adding,”
“Subtracting,” “Multiplying,” and “Dividing.” In each column, make a
list of vocabulary words that let you know which operation to use in
the expression. Then, solve the 26 practice problems at the bottom
of the page.

3.2 Simplifying ExpressionsAs we begin to model different real-life situations using mathematical
expressions, we will need to show the expressions using multiple
representations. Oftentimes a different, but equivalent, representation
of a mathematical expression will help shed light on different features
of the expression. For example, we might use the expression 20x + 36 to
represent the area of a rectangle. However, if we had written it as
4(5x + 9), we could then see two possible factors that could represent
the length (4) and width (5x + 9) of the rectangles. Both expressions
are equal to each other, but the second expression gives us a little
more information.

Instructions: Read through the examples to find out what is meant
by “like terms” and the steps you can use to combine them together.
Then watch the six-minute video to see some practice questions in
action. Finally, it is your turn to solve the 15 practice problems
at the bottom of the page.

Instructions: Read through the passage to see how simplifying
products and quotients differs from the sums and differences. Watch
the review video and then solve the 15 practice problems at the end
of the passage.

3.3 Evaluating ExpressionsTo better understand how and what an algebraic expression represents,
it is helpful to look at the value of the expression depending on the
value of the variable. For example, we are given the expression 3x + 5
to represent the total cost of visiting a fair, where the variable x
represents the number of rides or activities. If we know someone took
part in 11 rides or activities, we can now calculate the total cost.

3x + 53(11) + 533 + 538

This expression is equal to 38 when x = 11. That means that this
person spent $38 to go to the fair and participate in 11 rides or
activities. The value of the expression will change as the value of x
changes.

In this subunit, you will practice evaluating different expressions
and formulas and seeing how the value changes as the variables change.

Instructions: Read through the examples on pages 179 - 182,
beginning with example 1. Focus on the red sections that share the
steps to follow when evaluating. Then go to page 183 and complete
problems 1 - 12 and 29 - 38. The answers can be found on pages 185 -

Terms of Use: This resource is in the public domain. It is
attributed to Space Math @ NASA. The original version can be found
here.

3.4 Solving EquationsIn this subunit, we will grow from expressions to equations. Instead of
being able to plug in multiple values for the variable in expressions,
we will now be able to solve for a certain solution in an equation. This
subunit starts with solving two-step equations and then builds to
equations with multiple steps, including steps that involve combining
like terms and the distributive property.

Instructions: While watching the video, copy the equations,
practice showing the steps, and then check algebraically. For
example, if you were solving the equation 3x – 5 = 25, you need to
show the algebraic steps to prove that when x = 10, the equation
will be true. Then, when you check your work, you will replace the x
with the answer and evaluate to ensure that it is correct. Here is
an example of checking algebraically.

3x – 5 = 25
3(10) – 5 = 25
30 – 5 = 25
25 = 25

Watching this video and practicing the equations should take
approximately 15 minutes.

Instructions: Read the examples of how to change equations into
two-step equations. Then solve number 1, a - p in the “Review
Questions” section.

Reading the examples and solving the problems should take
approximately 45 minutes.

Standards Addressed (Common Core):

- [CCSS.Math.Content.7.EE.B.3](http://www.corestandards.org/Math/Content/7/EE/B/3)
- [CCSS.Math.Content.7.EE.4a](http://www.corestandards.org/Math/Content/7/EE/B/4/a)
Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 Unported
License](http://creativecommons.org/licenses/by-nc-sa/3.0/). It is
attributed to CK-12 Foundation and Barbara Greer. The original
version can be found
[here](http://www.ck12.org/user:YmdyZWVyQG1pdGFjYWRlbXkub3Jn/section/Two-Step-Equations/).

Instructions: Scroll down to page 337 and complete odd problems
49 - 59, using the same skills you used to solve the integer
equations. The answers can be found on pages 339 - 340. Use them to
check your work.

Instructions: Scroll down to page 213 and complete odd problems
17 - 51. Be sure to show an algebraic check as well. You can find
examples of algebraic checks on pages 210 through 212, labeled
“Check,” as well as in Subunit 3.4.1 of this course. The answers can
be found on page 214 and page 215. Use them to check your work.

3.5 Solving Word Problems and Writing EquationsUsing all of the skills we have developed to write expressions and
solve equations, we will build equations from word problems and solve
and discuss what the solutions mean in terms of the problem. A wide
variety of problems can be modeled using equations. In this subunit, you
will discover several different types and build skills for writing and
solving any type of equation involving one variable.

Instructions: Read this lesson to discover how the perimeter
formula can be used to create algebraic equations to solve. Complete
questions 14 - 16 of “Homework 55A” on page 7 after the reading. The
answers follow on page 9.

Instructions: In this section, you will write equations and define
variables in terms of the story problems given. After reading the
concession stand example, write equations to represent the six
practice problems. You do not have to solve the equations in this
section.

Reading this example and writing the equations should take
approximately 30 minutes.

Instructions: Skip the “Unit Conversion” section at the beginning
of this webpage. Begin reading when you see the title “Using
Algebraic Models.” While reading the remainder of the text, take
note of key vocabulary terms that help convert words into equations.
Then, create equations and solve the 10 problems under “Problem
Set.”

3.6 InequalitiesImagine that you have $300 to go shopping for school clothes. The total
of all the items you want to purchase must be less than or equal to
$300. It would be OK to get to the register and have a total of $238 or
$287 or even $199. As long as the total is not more than $300, you have
enough money to cover the costs. This is an example of an inequality.
This subunit will use your equation-solving skills to now solve
inequalities and graph the solutions.

Instructions: Explore the examples in the reading to see how
multiplying and dividing inequalities by negative numbers affects
the outcome of the solution. Then, solve the two example problems
before viewing the video solutions.

Reading this explanation, solving the problems, and watching the
videos should take approximately 30 minutes.

Standards Addressed (Common Core):

- [CCSS.Math.Content.7.EE.B.4b](http://www.corestandards.org/Math/Content/7/EE/B/4/b)
Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 Unported
License](http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_US).
It is attributed to [John Redden](http://www.openalgebra.com/). The
original version can be found
[here](http://www.openalgebra.com/2012/11/introduction-to-inequalities-and.html).

Instructions: This reading will introduce you to the notation and
graphing of inequalities. Be sure to note how the symbols are
connected with the open and closed circles for graphing. Solve the
17 practice problems at the bottom of the page.

Reading this selection and solving the practice problems should
take approximately 30 minutes.

Instructions: As the game begins, you will be given an inequality.
Your job is to hit asteroids with numbers that would be a solution
to the inequality. To play this game, you will use the arrow keys
and the space bar. You will use the space bar to hit the target.

Instructions: This is a series of practice problems for working
with inequalities. Complete all of the problems until you come to
the section entitled “Absolute Value Equations.” Note that this
activity covers the material you need to know for Subunit 3.6.1.1
and Subunit 3.6.1.2.

Completing this activity should take approximately 45 minutes.

Standards Addressed (Common Core):

- [CCSS.Math.Content.7.EE.B.4b](http://www.corestandards.org/Math/Content/7/EE/B/4/b)
Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 Unported
License](http://creativecommons.org/licenses/by-nc-sa/3.0/). It is
attributed to CK-12 Foundation. The original version can be found
[here](http://www.ck12.org/section/Inequalities/).

Instructions: After reading the lesson, write in complete sentences
why you might need to graph the solution to an inequality. Then
watch the Khan Academy video. Finally, solve the 15 practice
problems at the end of the passage. Note that this explanation
covers the material you need to know for Subunit 3.6.1.1 and Subunit
3.6.1.2.

Reading this lesson, taking notes, watching the video, and solving
the problems should take approximately 45 minutes.

3.6.1.2 Less Than or Equal To and Greater Than or Equal ToNote: This subunit is covered by the activity assigned beneath Subunit
3.6.1.1. Focus specifically on sections that include the symbols ≤ or ≥
and how graphing inequalities is different when these symbols are
included.

- [CCSS.Math.Content.7.EE.B.4b](http://www.corestandards.org/Math/Content/7/EE/B/4/b)
Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-ShareAlike 3.0 Unported
License](http://creativecommons.org/licenses/by-nc-sa/3.0/). It is
attributed to CK-12 Foundation and Jack Hatert. The original version
can be found
[here](http://www.ck12.org/user:amhhdGVydEB5c3NjaG9vbHMub3Jn/section/Solving-Inequalities/).